This invention relates to the art of testing container end closures for leakage.
Various apparatus exist for testing structures such as container end closures or the like by introducing a gas into a confined area in which the end closure is placed, and recording gas seepage or leakage therethrough. U.S. Pat. No. 3,499,314, issued on Mar. 10, 1970, discloses a testing apparatus wherein an end closure is tested in a cell or chamber formed by a vertically reciprocable upper chambered member and a fixed lower chambered member having seating means therein. The seated end closure is seated in registered fashion with the lower chambered member and sealedly divides the test chamber into two sections. High-pressure gas is supplied into one section while the other is simultaneously purged to the atmosphere to thereby flex the end so that gas leakage can be monitored or sensed in the other section, and leakers can be identified and ejected from the testing system.
U.S. Pats. Nos. 3,875,789 and 3,875,790, each issued on Apr. 8, 1975, disclose similar but improved closure testing apparatus capable of testing an end closure having a displaceable member covering or closing an aperture therein and sealed to the closure body by a distensible sealant material, such as, for example, a metal button down end closure having displaceable opening tabs or buttons sealed thereto by a plastisol, hot melt or other plastic sealant material. The disclosed improved apparatus provide the test chamber with means for effecting a separation between the end closures and their displaceable members or buttons, which include a resisting surface for holding one portion of the end closure in a substantially fixed position while the rest of the end closure is moved away from the buttons. The lower chambered member includes seating means for seating the end closure paratus closes down upon a portion of end closure seated on the seating means, the upper chambered member forces a portion of the end closure downward against spring pressure, and provides a temporary separation between the button and the end closure.
A problem with the prior art apparatus is that loss of registration of the end closure with respect to the lower chambered member seating means sometimes occurs when the upper chambered member is moved vertically upward from the lower chambered member. Although the upper section of the test chamber is purged to the atmosphere during testing, after testing, as the upper chambered member is raised from the end closure and from the lower chambered member, a lifting vacuum is sometimes created in the upper chambered member. This lifting vacuum sometimes moves or lifts the end closure and destroys its registered seated position. This movement is premature and undesirable because it makes it difficult for discharge mechanisms to find, take hold of and move tested end closures to discharge them from the test chamber. It can cause jams and prevents continuous operation of the apparatus. Loss of registration is additionally sometimes created in the improved apparatus of U.S. Pats. Nos. 3,875,789 and 3,875,790, due to sudden upward lurches of the end closure seating means when upward spring force under the end closure suddenly overcomes tackiness between the end closure and occasional accumulated deposits of tacky material such as vaporized plasticisor on the lower chambered member.